1 files changed, 124 insertions, 0 deletions
diff --git a/pgm5/prodcons.d/prodcons.c b/pgm5/prodcons.d/prodcons.c
new file mode 100644
index 0000000..665c744
--- /dev/null
+++ b/pgm5/prodcons.d/prodcons.c
@@ -0,0 +1,124 @@
+/* The classic producer-consumer example.
+   Illustrates mutexes and conditions.
+   All integers between 0 and 9999 should be printed exactly twice,
+   once to the right of the arrow and once to the left. */
+
+#include <stdio.h>
+#include <pthread.h>
+
+#define BUFFER_SIZE 16
+
+/* Circular buffer of integers. */
+
+struct prodcons
+{
+  int buffer[BUFFER_SIZE];	/* the actual data */
+  pthread_mutex_t lock;		/* mutex ensuring exclusive access to buffer */
+  int readpos, writepos;	/* positions for reading and writing */
+  pthread_cond_t notempty;	/* signaled when buffer is not empty */
+  pthread_cond_t notfull;	/* signaled when buffer is not full */
+};
+
+/* Initialize a buffer */
+static void
+init (struct prodcons *b)
+{
+  pthread_mutex_init (&b->lock, NULL);
+  pthread_cond_init (&b->notempty, NULL);
+  pthread_cond_init (&b->notfull, NULL);
+  b->readpos = 0;
+  b->writepos = 0;
+}
+
+/* Store an integer in the buffer */
+static void
+put (struct prodcons *b, int data)
+{
+  pthread_mutex_lock (&b->lock);
+  /* Wait until buffer is not full */
+  while ((b->writepos + 1) % BUFFER_SIZE == b->readpos)
+    {
+      pthread_cond_wait (&b->notfull, &b->lock);
+      /* pthread_cond_wait reacquired b->lock before returning */
+    }
+  /* Write the data and advance write pointer */
+  b->buffer[b->writepos] = data;
+  b->writepos++;
+  if (b->writepos >= BUFFER_SIZE)
+    b->writepos = 0;
+  /* Signal that the buffer is now not empty */
+  pthread_cond_signal (&b->notempty);
+  pthread_mutex_unlock (&b->lock);
+}
+
+/* Read and remove an integer from the buffer */
+static int
+get (struct prodcons *b)
+{
+  int data;
+  pthread_mutex_lock (&b->lock);
+  /* Wait until buffer is not empty */
+  while (b->writepos == b->readpos)
+    {
+      pthread_cond_wait (&b->notempty, &b->lock);
+    }
+  /* Read the data and advance read pointer */
+  data = b->buffer[b->readpos];
+  b->readpos++;
+  if (b->readpos >= BUFFER_SIZE)
+    b->readpos = 0;
+  /* Signal that the buffer is now not full */
+  pthread_cond_signal (&b->notfull);
+  pthread_mutex_unlock (&b->lock);
+  return data;
+}
+
+/* A test program: one thread inserts integers from 1 to 10000,
+   the other reads them and prints them. */
+
+#define OVER (-1)
+
+struct prodcons buffer;
+
+static void *
+producer (void *data)
+{
+  int n;
+  for (n = 0; n < 10000; n++)
+    {
+      printf ("%d --->\n", n);
+      put (&buffer, n);
+    }
+  put (&buffer, OVER);
+  return NULL;
+}
+
+static void *
+consumer (void *data)
+{
+  int d;
+  while (1)
+    {
+      d = get (&buffer);
+      if (d == OVER)
+	break;
+      printf ("---> %d\n", d);
+    }
+  return NULL;
+}
+
+int
+main (void)
+{
+  pthread_t th_a, th_b;
+  void *retval;
+
+  init (&buffer);
+  /* Create the threads */
+  pthread_create (&th_a, NULL, producer, 0);
+  pthread_create (&th_b, NULL, consumer, 0);
+  /* Wait until producer and consumer finish. */
+  pthread_join (th_a, &retval);
+  pthread_join (th_b, &retval);
+  return 0;
+}